<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        //可以给形参赋初始值
        let add = (a,b,c = 3) => {
            return a+b+c;
        }
        console.log(add(1,2));

        //可以和解构赋值结合使用
        function connect({host = "127.0.0.1",username,password,port}){
            console.log(host);
            console.log(username);
            console.log(password);
            console.log(port);
        }

        connect({
            host:'localhost',
            username:'root',
            password:'root',
            port:3306
        })
    </script>
</body>
</html>